Saute mushrooms in butter and oil for 3-5 minutes, stirring occasionally. Add red wine and simmer for a few minutes. Add beef broth and simmer to reduce a bit, about 5 minutes. Combine flour and cold water and whisk until smooth. Stir into the mushrooms until well blended. Season to taste and simmer for about 1 minute, until thickened. If too thick, add a bit more broth. Add parsley.